This application claims the priority of German Patent Application No. 197 37 305.4 filed Aug. 27, 1997 and PCT/EP98/05020, filed Aug. 7, 1998, the disclosures of which are expressly incorporated by reference herein.
The present invention relates to a gear-shift device for a change-speed gearbox, and more particularly, to a gear-shaft device having a shift actuator which is arranged rotatably and axially displaceably with respect to a central axis of a housing, having a selection actuator which is coaxial with respect to the central axis and is arranged rotatably relative to the housing, having an actuator which is coaxial with respect to the central axis and is arranged such that it can be displaced exclusively axially relative to the housing, having means for fixing the selection actuator with regard to the housing in the longitudinal directions of the central axis, having an engageable and disengageable brake for fixing the selection actuator with regard to the housing in the circumferential directions of the central axis, having an auxiliary transmission for converting a reciprocating motion into a rotary motion.
A gear-shift device is described in DE 196 10 104 A1.
In this known gear-shift device, a selection control sleeve is arranged concentrically to a shift control shaft and is connected to the latter by the auxiliary transmission in the form of a guide plate/guide pin arrangement. The shift control shaft is connected, by a rod-like actuator, to a pressure-medium servomotor of the axial-piston type, while an electromagnet is used for actuating the brake acting on the selection control sleeve. The selection control sleeve is fixed immovably with regard to the housing in the longitudinal directions of the central axis, while the shift control shaft is latched by a latching device in its significant rotation-angle positions assigned to a respective shift gate for shifting one or two gears.
In this known gear-shift device according to DE 196 10 104 A1, it is already possible to shift gear from a current gear into a new gear while skipping at least one intermediate gear by causing the shift control shaft to execute a linear actuation motion which oscillates about the middle significant position and thus alternately engaging and disengaging the brake of the actuation control sleeve when passing through the middle significant position. In order, when skipping gears, to avoid collision between the synchronization devices assigned to these gears and the shift control shaft, a certain free travel is provided for the shift control shaft.
DE 41 37 142 A1 describes a gear-shift device of another type, in which an electric motor is connected, by way of a screw mechanism for converting a rotary motion into a reciprocating motion, to a gear-shift rod which is mounted rotatably and axially displaceably in a housing and can be fixed with regard to the housing by an engageable and disengageable brake device. Thereby, the gear-shift rod is arranged to be exclusively axially displaceable in the engaged position of the brake, but in the disengaged position of the brake is arranged to be both axially displaceable and rotatable with regard to the housing. The gear-shift rod is directly connected to the motor shaft of the electric motor by a coupling which can be engaged and disengaged in opposite directions to the brake. When changing between selecting and shifting, both coupling and brake have to be changed over and the electric motor stopped.
DE 43 09 027 A1 describes yet a further gear-shift device of another type, in which a gear-shift shaft, which is arranged rotatably and axially displaceably with regard to a pressure-medium cylinder, can be moved by a first axial piston of the pressure-medium cylinder directly in the directions of the gear-shift shaft axis for shifting the gears. A second axial piston of the pressure-medium cylinder, with the aid of an auxiliary transmission for converting a reciprocating motion into a rotary motion with regard to the gear-shift shaft axis, causes the gear-shift shaft to perform rotary movements for selecting the shift gates.
An object underlying the present invention essentially consists in allowing a gear-shift device likewise to skip at least one intermediate gear when shifting from a current gear into a new gear but dispensing with or largely avoiding special free travel for the shift actuator.
This object has been advantageously achieved according to the present invention by a gear-shift device in which the shift actuator, when actuated into the rotation-angle position associated with the new gear, remains fixed immovably by the locking device in the longitudinal directions of the central axis of the housing. Thus, special free travel for the shift actuator, in order to avoid collision with synchronization devices during this actuation, is not required, because the linear movement required for selecting the new rotation-angle position is performed only by the third actuator, which is arranged such that it can be displaced exclusively axially with regard to the housing.
Another object underlying the present improve the known gear-shift device in such a way that the process reliability of the shift sequence is improved.
According to the present invention, the foregoing object has been achieved in an advantageous manner by proving that reciprocating motion into a rotary motion, and in which two of the three actuators are both arranged such that they are fixed in terms of movement with respect to one another, at least in the longitudinal directions of the central axis, and are connected to the third actuator by the auxiliary transmission, and an engageable and disengageable locking device is connected in terms of action both to the selection actuator and to the brake in such a manner that the selection actuator can be fixed with regard to the housing alternately either exclusively in the circumferential directions or exclusively in the longitudinal directions of the central axis, and in which the selection actuator is connected by the auxiliary transmission to the actuator which is arranged such that it can be displaced exclusively axially with regard to the housing, according to main patent 196 35 866, characterized in that a guide pin (42) is guided in a fixed shift guide plate (43) which represents the shift pattern of a manual shift lever, and in that the guide pin (42) is arranged in a manner fixed in terms of movement with regard to the shift actuator (9) and radially to the central axis (7xe2x80x947).
The fixed slotted shift guide, in which a guide pin arranged in a manner fixed in terms of motion with regard to the shift actuator is guided, ensures that it is only possible to change between shifting and selection in the positions determined by the internal structure of the gearbox. This improves the process reliability of the shift sequence. Moreover, it is possible to simplify the internal shift mechanism of the gearbox since the latching elements for the shifting and selection movement on the shift actuator can be omitted.
In a special embodiment of the gear-shift device according to the invention, the selection of the shifting or selection plane is incorporated into the operation of a slotted change-interlock guide interacting with a guide pin at the shift actuator. Depending on the respective end position of the slotted change-interlock guide, the shift actuator is free to move either only in the direction of selection or only in the direction of shifting. A sensor system for the positionally correct switching of the slotted change-interlock guide can be placed in the slotted change-interlock guide to minimize system tolerances. The slotted change-interlock guide can furthermore be controlled in such a way that the impulse produced by the change of direction between shifting and selection can be absorbed, thus keeping down mechanical loading.